Electrical problem with L1421, V2203 engine

[Hugo Habicht]

Hello,

my friend called me with his tractor broken down in the woods. "Release PTO" was the error message in the display. Turns out this was totally wrong, the fault was fuse 12 "key stop". We replaced the fuse, tractor started but died a short time later again.

I am looking for schematics for the L1421 from 2019 in another thread, but no success so far, a work shop manual would be helpful too but we will try to get that from the Kubota dealer tomorrow (public holiday here today).

My question at this stage is: does anybody know if the shutoff solenoid is powered while the engine is running or if it is powered to stop the engine?

Kind regards,
Hugo

 

[Hugo Habicht]

Ok, a bit further now. It seems the solenoid is powered while the engine is running.

Would anybody know if the solenoid current is being reduced electronically by the ECU after the solenoid is engaged?

 

[PoTreeBoy]

Ok, a bit further now. It seems the solenoid is powered while the engine is running.

Would anybody know if the solenoid current is being reduced electronically by the ECU after the solenoid is engaged?

I don't know about that, but solenoids on some of the newer models have two coils and an internal switch that disconnects the pull-in coil, when the plunger moves.

 

[Hugo Habicht]

Yes, I thought that too. But we have the coil out now, there is 0.8A flowing at 13.8V and no force on the plunger whatsoever. And the fuse fails after a few minute. I am really confused now what is happening. This just does not make sense.

 

[Hugo Habicht]

Ok, a step further. Found the engine manual.

The solenoid has two coils against the chassis, so two coil design as PoTreeBoy pointed out. I had measured between the two pins, that was my mistake.

So the pull coil has about 0.38 Ohms, the hold coil about 17 Ohms. The pull coil has it's own switch that disconnects it when pulled in.

So the coil works, but is the pull coils current too high?

Why is the fuse blowing all the time?

There must be something else connected to the fuse, I need the workshop manual of the tractor.

 

[Russell King]

I think the solenoids as described above have three wires, so that may help determine how it works.

Some may also use the case as the ground point and have only one or two wires.

Some tractors hold open while running and others pull closed when turned off.

So Kubota has not made it easy to figure out really. I have none on my tractor so can’t say much more about it!

How many wires is on yours and what are the color designations?

 

[Russell King]

Reading the bold statement in your manual’s information above makes me think the pull in coil is NOT being properly released before the fuse is blown out!

 

[Hugo Habicht]

Reading the bold statement in your manual’s information above makes me think the pull in coil is NOT being properly released before the fuse is blown out!

No, solenoid works fine. It is pulled in in under 100ms and the current goes down to 0.8A. You cannot have high current flowing for longer because the internal switch disconnects the pull coil.

In this case the solenoid stays energised while engine running.

So current must flow elsewhere. I built my friend a test cable to measure the current over the fuse. He lives almost an hour away from me, so fault finding is not straightforward. He has the faulty tractor and I have the test equipment

 

[North Idaho Wolfman]

On that style coil there are normally 2 feeds one from the starter and one from the ignition.
When cranking the coil gets a signal from the starter to pull in then the signal from the ignition feeds the solenoid.
There is normally a relay that controls the pull in coil and that fuse he keeps blowing is probably the feed for the relay.
There is also a buffer circuit on those solenoids that has a capacitor and a diode in it to mitigate backfeed voltage on power down.
I would say his issue is more than likely a bad stop solenoid, but can't rule out a bad relay as a possible cause, or even a shorting wire.

 

[Hugo Habicht]

On that style coil there are normally 2 feeds one from the starter and one from the ignition.
When cranking the coil gets a signal from the starter to pull in then the signal from the ignition feeds the solenoid.
There is normally a relay that controls the pull in coil and that fuse he keeps blowing is probably the feed for the relay.

In this case both coils are driven by the ECU. Not sure why they do it this way, maybe to check the current for faults.

Keep in mind, this schematics is from engine manual, it may be different on the tractor.

He will measure the current now with the little adapter above and hopefully we will get a workshop manual and we work from there.

Glad my friend called with the solenoid, I was pretty sure that was the fault, it would have been an expensive exercise and another three days delay for the part to arrive. My friend has holidays and had planned to do a lot of work with the Kubota, so very unfortunate the whole thing.

 

[North Idaho Wolfman]

In this case both coils are driven by the ECU. Not sure why they do it this way, maybe to check the current for faults.

Keep in mind, this schematics is from engine manual, it may be different on the tractor.

Then you down to bad solenoid (most likely), or a chaffed wire intermittently shorting, or a bad ECU, one can hope not that.

 

[Hugo Habicht]

Then you down to bad solenoid (most likely), or a chaffed wire intermittently shorting, or a bad ECU, one can hope not that.

From what I checked the solenoid is fine. Pulls and holds as it should, holding current is 0.8A.

We checked for chafed wires but could not find anything. Everything looks pristine. Tractor is 6 years old, 200 hours, first owner.

And yes, you are right, I hope it is not the ECU.

I think there are other things on that fuse, for example "disengage PTO" appears on display when fuse is blown. But without proper documentation I'd be wasting my time looking further.

 

[North Idaho Wolfman]

There is one thing that you can do for intermittent issues is install a circuit breaker in place of the fuse.
Helps tremendously with troubleshooting.